Even though we usually think of water as running downhill, it can indeed flow upwards
using a process called capillary action. This is the very scientific principal that
explains how water goes from the soil upwards into the stem of plants. Plants contain
many vein like tubes that carry water from the plant's roots upwards to the plant's
highest leafs via capillary action. Try this experiment to see capillary action
in action.
- Wrap the plastic wrap around the knitting needle and then tape the edges so that
you have formed a tube. Remember, the narrower the tube, the more pronounced the
capillary effect will be.
- Once you have taped the plastic wrap, pull out the knitting needle. Make sure that
the new plastic tube is not bent and is open at both ends.
- Now pour a little of the food coloring into a glass half filled with water.
- Now place your plastic tube into the glass of water.
- Examine the tube carefully. The dye should climb up the tube above the
level of the liquid in the glass.
Now try the same experiment with varying levels of water in the glass. Does this
make a difference?